The proposed investigation focuses on longitudinal phonological development in normal (ages 2 mos.- 3 years), hearing-impaired (6 mos.-7 years), and Down's syndrome (3 mos.- 7 years) children. Over 80% of the data on which the investigation is based have already been collected; these data are of three types: a. 102 phonetically transcribed tapes of babbling utterances, b. 118 phonetically transcribed and computer-coded tapes of productions of single words; c. 64 tapes of conversational speech, glossed orthographically but not transcribed phonetically. The data have been collected at three-month intervals over the past four years. During the proposed grant period, all three sets of data will be transcribed, computer-coded, and entered into a computerized storage-and-retrieval system to facilitate analysis. In addition, meaningful-speech data will be collected from five hearing-impaired and Down's syndrome subjects who are still in the babbling stage. The data will be analyzed in a generative framework, focusing on individual patterns of development as measured by 1. the presence of certain phonological processes and 2. the presence/absence of the phonemes and phonemic contrasts of adult English. Special attention will be given to the range and type of variation evident in the speech of the abnormal population since previous studies have provided us with little knowledge in this area. Comparison between the babbling and meaningful-speech data will be made in terms of preferences for sound types and sound sequences. Once transcribed and stored in the computer, the data base will be documented in detail in order to make it available to other researchers in the filed.